explicitly set latex backend to latexmk

lua/plugins/latex.lua

@@ -8,6 +8,7 @@ return {
     init = function()
       -- VimTeX configuration goes here
       vim.g.vimtex_view_method = "skim"
+      vim.g.vimtex_compiler_method = "latexmk"
     end,
   },
 }